Sulfonates, polymers, resist compositions and patterning process

ABSTRACT

A sulfonate compound having formula (1) is novel wherein R 1  to R 3  are H, F or C 1-20  alkyl or fluoroalkyl, at least one of R 1  to R 3  contains F. A polymer comprising units derived from the sulfonate compound is used as a base resin to formulate a resist composition which is sensitive to high-energy radiation, maintains high transparency at a wavelength of up to 200 nm, and has improved alkali dissolution contrast and plasma etching resistance

This Nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No(s). 2003-032584 filed in JAPAN on Feb. 10,2003, the entire contents of which are hereby incorporated by reference.

This invention relates to polymers useful as the base resin in resistcompositions suited for microfabrication and sulfonic acid esters usefulas the starting monomers for the polymers. It also relates to resistcompositions, especially chemical amplification resist compositionscomprising the polymers, and a patterning process using the same.

BACKGROUND OF THE INVENTION

In the drive for higher integration and operating speeds in LSI devices,the pattern rule is made drastically finer. The rapid advance towardfiner pattern rules is grounded on the development of a projection lenswith an increased NA, a resist material with improved performance, andexposure light of a shorter wavelength. To the demand for a resistmaterial with a higher resolution and sensitivity, chemicalamplification positive working resist materials which are catalyzed byacids generated upon light exposure are effective as disclosed in U.S.Pat. Nos. 4,491,628 and 5,310,619 (JP-B 2-27660 and JP-A 63-27829). Theynow become predominant resist materials especially adapted for deep UVlithography.

Also, the change-over from i-line (365 nm) to shorter wavelength KrFlaser (248 nm) brought about a significant innovation. Resist materialsadapted for KrF excimer lasers enjoyed early use on the 0.30 micronprocess, passed through the 0.25 micron rule, and currently entered themass production phase on the 0.18 micron rule. Engineers have startedinvestigation on the 0.10 micron rule or less, with the trend toward afiner pattern rule being accelerated.

For ArF laser (193 nm), it is expected to enable miniaturization of thedesign rule to 0.13 μm or less. Since conventionally used novolac resinsand polyvinylphenol resins have very strong absorption in proximity to193 nm, they cannot be used as the base resin for resists. To ensuretransparency and dry etching resistance, some engineers investigatedacrylic and alicyclic (typically cycloolefin) resins as disclosed inJP-A 9-73173, JP-A 10-10739, JP-A 9-230595 and WO 97/33198.

With respect to F₂ laser (157 nm) which is expected to enable furtherminiaturization to 0.10 μm or less, more difficulty arises in insuringtransparency because it was found that acrylic resins which are used asthe base resin for ArF are not transmissive to light at all and thosecycloolefin resins having carbonyl bonds have strong absorption. It wasalso found that poly(vinyl phenol) which is used as the base resin forKrF has a window for absorption in proximity to 160 nm, so thetransmittance is somewhat improved, but far below the practical level.

Since carbonyl groups and carbon-to-carbon double bonds have absorptionin proximity to 157 nm as mentioned above, reducing the number of suchunits is contemplated to be one effective way for improvingtransmittance. It was recently found that the transmittance in the F₂region is outstandingly improved by introducing fluorine atoms into basepolymers.

It was reported in SPIE 2001, Proceedings 4345-31, “Polymer design for157 nm chemically amplified resists” that in resist compositionscomprising a copolymer of tert-butyl α-trifluoromethylacrylate with5-(2-hydroxy-2,2-bistrifluoromethyl)ethyl-2-norbornene and a copolymerof tert-butyl α-trifluoromethylacrylate with4-(2-hydroxy-2,2-bistrifluoromethyl)methylstyrene, the absorbance of thepolymer at 157 nm is improved to about 3. However, these resins arestill insufficient in transparency because it is believed that anabsorbance of 2 or less is necessary to form a rectangular pattern at afilm thickness of at least 2,000 Å through F₂ exposure.

The inventor found that incorporating fluorinated vinyl sulfonate unitsinto the above-described α-trifluoromethylacrylate polymers improves thetransparency while maintaining the substrate adhesion and developeraffinity of the resins. These systems still have an absorbance ofapproximately 2.

SUMMARY OF THE INVENTION

An object of the invention is to provide a novel polymer having a hightransmittance to vacuum ultraviolet radiation of up to 300 nm,especially F₂ (157 nm), Kr₂ (146 nm), KrAr (134 nm) and Ar₂ (126 nm)laser beams, and useful as the base resin in a resist composition, and anovel sulfonic acid ester useful as the starting monomer for thepolymer. Another object is to provide a resist composition, especially achemical amplification resist composition, comprising the polymer, and apatterning process using the same.

It has been found that when a polymer comprising units derived from amonomer having a fluorinated alkyl group introduced on a sulfonate sidechain is used as a base resin, the resulting resist composition,especially chemically amplified resist composition is drasticallyimproved in contrast and adhesion without detracting from transparency.

In a first aspect, the present invention provides a sulfonate compoundhaving the following general formula (1).

Herein R¹ to R³ each are hydrogen, fluorine or a straight, branched orcyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, atleast one of R¹ to R³ contains fluorine, R¹ and R², R¹ and R³, or R² andR³, taken together, may form a ring, each of R¹ to R³ is a straight orbranched alkylene or fluorinated alkylene group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms, when they form a ring.

In a second aspect, the present invention provides a polymer comprisingrecurring units of the following general formula (2) and having a weightaverage molecular weight of 1,000 to 500,000.

Herein R¹ to R³ are as defined above.

In a preferred embodiment, the polymer further comprises recurring unitsof at least one type selected from the following general formulae (3a)to (3f).

Herein R⁴, R⁵, R⁷, R⁸ and R¹⁵ each are a single bond or a straight,branched or cyclic alkylene or fluorinated alkylene group of 1 to 20carbon atoms, R⁶, R⁹, R¹² and R¹⁸ each are hydrogen or an acid labilegroup, R¹⁰, R¹¹, R¹³, R¹⁴, R¹⁶ and R¹⁷ each are hydrogen, fluorine, astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20carbon atoms, at least one of R¹⁶ and R¹⁷ contains at least one fluorineatom, R¹⁹ is a straight, branched or cyclic fluorinated alkyl group of 1to 20 carbon atoms, “a” and “b” each are 1 or 2.

In a preferred embodiment, the polymer further comprises recurring unitsof the following general formula (4).

Herein R²⁰ is a methylene group, oxygen atom or sulfur atom, R²¹ to R²⁴each are hydrogen, fluorine, —R²⁵—OR²⁶, —R²⁵—CO₂R²⁶ or a straight,branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbonatoms, at least one of R²¹ to R²⁴ containing —R²⁵—OR²⁶ or —R²⁵—CO₂R²⁶,R²⁵ is a single bond or a straight, branched or cyclic alkylene orfluorinated alkylene group of 1 to 20 carbon atoms, R²⁶ is hydrogen, anacid labile group, adhesive group or a straight, branched or cyclicfluorinated alkyl group of 1 to 20 carbon atoms which may contain ahydrophilic group such as hydroxyl, and c is 0 or 1.

More preferably, the recurring units of formula (4) have a structure ofthe following general formula (4a) or (4b).

Herein R²⁶ is as defined above, R²⁷ to R³⁰ each are hydrogen, fluorineor an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms, at leasteither one of R²⁷ and R²⁸ contains at least one fluorine atom, and atleast either one of R²⁹ and R³⁰ contains at least one fluorine atom.

In a preferred embodiment, the polymer further comprises recurring unitsof the following general formula (5).

Herein R³¹ is hydrogen, fluorine or a straight, branched or cyclic alkylor fluorinated alkyl group of 1 to 20 carbon atoms, R³² is a single bondor a straight, branched or cyclic alkylene or fluorinated alkylene groupof 1 to 20 carbon atoms, R³³ is hydrogen or an acid labile group, R³⁴ isfluorine or a straight, branched or cyclic fluorinated alkyl group of 1to 20 carbon atoms, d is 1 or 2, and e is an integer of 0 to 4,satisfying 1≦d+e≦5.

More preferably, the recurring units of formula (5) have the followingformula (5a) or (5b).

Herein R³³ is as defined above, R³⁵ to R⁴⁰ each are hydrogen, fluorineor an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms, at leasteither one of R³⁵ and R³⁶ contains at least one fluorine atom, at leasteither one of R³⁷ and R³⁸ contains at least one fluorine atom, and atleast either one of R³⁹ and R⁴⁰ contains at least one fluorine atom.

In another preferred embodiment, the polymer further comprises recurringunits of the following general formula (6).

Herein R⁴¹ to R⁴³ each are hydrogen, fluorine or a straight, branched orcyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, and R⁴⁴is hydrogen, an acid labile group, an adhesive group or a straight,branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms whichmay contain a hydrophilic group such as hydroxyl. Most often R⁴³ istrifluoromethyl.

In a third aspect, the present invention provides a resist compositioncomprising the polymer defined above, and specifically a chemicallyamplified positive resist composition comprising (A) the polymer definedabove, (B) an organic solvent, and (C) a photoacid generator. The resistcomposition may further comprise (D) a basic compound and/or (E) adissolution inhibitor.

In a fourth aspect, the present invention provides a process for forminga resist pattern comprising the steps of applying the above resistcomposition onto a substrate to form a coating; heat treating thecoating and then exposing it to high-energy radiation in a wavelengthband of 100 to 180 nm or 1 to 30 nm through a photomask; and optionallyheat treating the exposed coating and developing it with a developer.The high-energy radiation is typically an F₂ laser beam, Ar₂ laser beamor soft x-ray.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Polymer

For improving the transmittance in proximity to 157 nm, reducing thenumber of carbonyl groups and/or carbon-to-carbon double bonds iscontemplated to be one effective way. It was also found that introducingfluorine atoms into base polymers makes a great contribution to improvedtransmittance. In fact, poly(vinyl phenol) having fluorine introduced inits aromatic rings offers a transmittance nearly on a practicallyacceptable level (see JP-A 2001-146505). However, this base polymer wasfound to turn to be negative upon exposure to high-energy radiation asfrom an F₂ laser, interfering with its use as a practical resist. On theother hand, those polymers obtained by introducing fluorine into acrylicresins or polymers containing in their backbone an alicyclic compoundoriginating from a norbornene derivative were found to have a hightransparency and eliminate the negative turning problem. However, anincreased rate of introduction of fluorine into a resin to enhance thetransparency thereof tends to compromise the adhesion of resin tosubstrate or the penetration of a developer.

It has been found that sulfonates have a relatively high transmittanceat about 157 nm despite two sulfur-oxygen double bonds, and a resincomprising such sulfonate units is dramatically improved in substrateadhesion and developer penetration as compared with the aforementionedfluorinated polymers. Specifically, using a base polymer comprisingunits of the general formula (2) derived from a sulfonate compound ofthe general formula (1) which is obtained by introducing fluorine into atertiary alkyl ester of sulfonic acid which inherently lacks stability,a resist composition having an acid eliminating ability is obtainedwhile maintaining stability.

Herein R¹ to R³ each are hydrogen, fluorine or a straight, branched orcyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, atleast one of R¹ to R³ contains fluorine, a pair of R¹ and R², a pair ofR¹ and R³, or a pair of R² and R³, taken together, may form a ring, eachof R¹ to R³ is a straight or branched alkylene or fluorinated alkylenegroup of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, whenthey form a ring.

While the polymer or high molecular weight compound of the invention isdefined as comprising recurring units of the general formula (2),recurring units of at least one type selected from the general formulae(3a) to (3f) and/or recurring units of the general formula (4) and/orrecurring units of the general formula (5) and/or recurring units of thegeneral formula (6) are preferably incorporated in order to improve thedissolution contrast, substrate adhesion, dry etching resistance andother properties of the resist.

Herein R⁴, R⁵, R⁷, R⁸ and R¹⁵ each are a single bond or a straight,branched or cyclic alkylene or fluorinated alkylene group of 1 to 20carbon atoms, R⁶, R⁹, R¹² and R¹⁸ each are hydrogen or an acid labilegroup, R¹⁰, R¹¹, R¹³, R¹⁴, R¹⁶ and R¹⁷ each are hydrogen, fluorine, astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20carbon atoms, at least one of R¹⁶ and R¹⁷ contains at least one fluorineatom, R¹⁹ is a straight, branched or cyclic fluorinated alkyl group of 1to 20 carbon atoms, “a” and “b” each are 1 or 2.

Herein R²⁰ is a methylene group, oxygen atom or sulfur atom, R²¹ to R²⁴each are hydrogen, fluorine, —R²⁵—OR²⁶, —R²⁵—CO₂R²⁶ or a straight,branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbonatoms, at least one of R²¹ to R²⁴ containing —R²⁵—OR²⁶ or —R²⁵—CO₂R²⁶,R²⁵ is a single bond or a straight, branched or cyclic alkylene orfluorinated alkylene group of 1 to 20 carbon atoms, R²⁶ is hydrogen, anacid labile group, adhesive group or a straight, branched or cyclicfluorinated alkyl group of 1 to 20 carbon atoms which may contain ahydrophilic group such as hydroxyl, and c is 0 or 1.

Herein R³¹ is hydrogen, fluorine or a straight, branched or cyclic alkylor fluorinated alkyl group of 1 to 20 carbon atoms, R³² is a single bondor a straight, branched or cyclic alkylene or fluorinated alkylene groupof 1 to 20 carbon atoms, R³³ is hydrogen or an acid labile group, R³⁴ isfluorine or a straight, branched or cyclic fluorinated alkyl group of 1to 20 carbon atoms, d is 1 or 2, and e is an integer of 0 to 4,satisfying 1≦d+e≦5.

Herein R⁴¹ to R⁴³ each are hydrogen, fluorine or a straight, branched orcyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, and R⁴⁴is hydrogen, an acid labile group, an adhesive group or a straight,branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms whichmay contain a hydrophilic group such as hydroxyl. Preferably, R⁴³ istrifluoromethyl.

The preferred recurring units of formula (4) are units of the followinggeneral formula (4a) or (4b).

Herein R²⁶ is as defined above, R²⁷ to R³⁰ each are hydrogen, fluorineor an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms, at leasteither one of R²⁷ and R²⁸ contains at least one fluorine atom, and atleast either one of R²⁹ and R³⁰ contains at least one fluorine atom.

The preferred recurring units of formula (5) are units of the followingformula (5a) or (5b).

Herein R³³ is as defined above, R³⁵ to R⁴⁰ each are hydrogen, fluorineor an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms, at leasteither one of R³⁵ and R³⁶ contains at least one fluorine atom, at leasteither one of R³⁷ and R³⁸ contains at least one fluorine atom, and atleast either one of R³⁹ and R⁴⁰ contains at least one fluorine atom.

More particularly, suitable straight, branched or cyclic alkyl groups of1 to 20 carbon atoms include, but are not limited to, methyl, ethyl,propyl, isopropyl, n-propyl, n-butyl, sec-butyl, tert-butyl,cyclopentyl, cyclohexyl, cyclohexylmethyl, 2-ethylhexyl, n-octyl,2-adamantyl, and (2-adamantyl)methyl, with those of 1 to 12 carbonatoms, especially 1 to 10 carbon atoms being preferred.

The fluorinated alkyl groups correspond to the foregoing alkyl groups inwhich some or all of the hydrogen atoms are replaced by fluorine atoms.Examples include, but are not limited to, trifluoromethyl,2,2,2-trifluoroethyl, 3,3,3-trifluoropropyl,1,1,1,3,3,3-hexafluoroisopropyl, and 1,1,2,2,3,3,3-heptafluoropropyl aswell as groups of the following formulae.

Herein, R⁴⁵ is a hydrogen atom, a fluorine atom or a straight, branchedor cyclic alkyl or fluorinated alkyl group of 1 to 10 carbon atoms, andf is an integer of 0 to 5.

Suitable straight, branched or cyclic alkylene groups of 1 to 20 carbonatoms correspond to the foregoing alkyl groups with one hydrogen atomeliminated. Suitable fluorinated alkylene groups are similar alkylenegroups which are partially or entirely substituted with fluorine atoms.

The acid labile groups represented by R⁶, R⁹, R¹², R¹⁸, R²⁶, R³³ and R⁴⁴are selected from a variety of such groups, preferably from among thegroups of the following formulae (7) to (9).

In formula (7), R⁴⁶ is a tertiary alkyl group of 4 to 20 carbon atoms,preferably 4 to 15 carbon atoms, or an oxoalkyl group of 4 to 20 carbonatoms. Suitable tertiary alkyl groups include tert-butyl, tert-amyl,1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl,1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl,1-ethyl-2-cyclohexenyl, and 2-methyl-2-adamantyl. Suitable oxoalkylgroups include 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and5-methyl-5-oxooxolan-4-yl. Letter g is an integer of 0 to 6.

Illustrative, non-limiting, examples of the acid labile group of formula(7) include tert-butoxycarbonyl, tert-butoxycarbonylmethyl,tert-amyloxycarbonyl, tert-amyloxycarbonylmethyl,1,1-diethylpropyloxycarbonyl, 1,1-diethylpropyloxycarbonylmethyl,1-ethylcyclopentyloxycarbonyl, 1-ethylcyclopentyloxycarbonylmethyl,1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

In formula (8), R⁴⁷ and R⁴⁸ are hydrogen or straight, branched or cyclicalkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms,for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl and n-octyl. R⁴⁹ is amonovalent hydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10carbon atoms, which may contain a hetero atom such as oxygen, forexample, straight, branched or cyclic alkyl groups and substituted onesof these alkyl groups in which some hydrogen atoms are substituted withhydroxyl, alkoxy, oxo, amino or alkylamino groups. Exemplary substitutedalkyl groups are shown below.

A pair of R⁴⁷ and R⁴⁸, a pair of R⁴⁷ and R⁴⁹, or a pair of R⁴⁸ and R⁴⁹may bond together to form a ring. Each of R⁴⁷, R⁴⁸ and R⁴⁹ is a straightor branched alkylene group of 1 to 18 carbon atoms, preferably 1 to 10carbon atoms, when they form a ring.

Of the acid labile groups of formula (8), straight or branched ones areexemplified by the following groups.

Of the acid labile groups of formula (8), cyclic ones are exemplified bytetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Of the groups of formula (8), ethoxyethyl, butoxyethyl and ethoxypropylare preferred.

In formula (9), R⁵⁰, R⁵¹ and R⁵² each are a monovalent hydrocarbongroup, typically a straight, branched or cyclic alkyl group of 1 to 20carbon atoms, which may contain a hetero atom such as oxygen, sulfur,nitrogen or fluorine. A pair of R⁵⁰ and R⁵¹, R⁵⁰ and R⁵², and R⁵¹ andR⁵², taken together, may form a ring with the carbon atom to which theyare bonded.

Examples of the tertiary alkyl group represented by formula (9) includetert-butyl, triethylcarbyl, 1-ethylnorbornyl, 1-methylcyclohexyl,1-ethylcyclopentyl, 2-(2-methyl)adamantyl, 2-(2-ethyl)adamantyl,tert-amyl, 1,1,1,3,3,3-hexafluoro-2-methyl-isopropyl, and1,1,1,3,3,3-hexafluoro-2-cyclohexyl-isopropyl as well as the groupsshown below.

Herein, R⁵³ is a straight, branched or cyclic alkyl group of 1 to 6carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, n-pentyl, n-hexyl, cyclopropyl, cyclopropylmethyl,cyclobutyl, cyclopentyl and cyclohexyl. R⁵⁴ is a straight, branched orcyclic alkyl group of 2 to 6 carbon atoms, such as ethyl, propyl,isopropyl, n-butyl, sec-butyl, n-pentyl, n-hexyl, cyclopropyl,cyclopropylmethyl, cyclobutyl, cyclopentyl and cyclohexyl. Each of R⁵⁵and R⁵⁶ is hydrogen, a monovalent hydrocarbon group of 1 to 6 carbonatoms which may contain a hetero atom, or a monovalent hydrocarbon groupof 1 to 6 carbon atoms which may be separated by a hetero atom. Thesegroups may be straight, branched or cyclic. The hetero atom is typicallyselected from oxygen, sulfur and nitrogen atoms and may be contained orintervene in the form of —OH, —OR⁵⁷, —O—, —S—, —S(═O)—, —NH₂, —NHR⁵⁷,—N(R⁵⁷)₂, —NH— or —NR⁵⁷— wherein R⁵⁷ is a C₁₋₅ alkyl group. Examples ofR⁵⁵ and R⁵⁶ groups include methyl, hydroxymethyl, ethyl, hydroxyethyl,propyl, isopropyl, n-butyl, sec-butyl, n-pentyl, n-hexyl, methoxy,methoxymethoxy, ethoxy and tert-butoxy.

Next, the adhesive groups represented by R²⁶ and R⁴⁴ are selected from avariety of such groups, preferably from among the groups of thefollowing formulae.

Herein, R⁵⁸ is a methylene group, oxygen atom or sulfur atom.

Illustrative examples of the units of formula (2) are given below,though not limited thereto.

Illustrative examples of the units of formulae (3a) to (3d) are givenbelow, though not limited thereto.

Herein R⁶, R⁹ and R¹⁸ are as defined above.

Illustrative examples of the units of formulae (4), (4a) and (4b) aregiven below, though not limited thereto.

Herein R²⁶ is as defined above.

Illustrative examples of the units of formulae (5), (5a) and (5b) aregiven below, though not limited thereto.

Herein R³³ is as defined above.

Besides, units as shown below may be incorporated in the inventivepolymers for the purpose of improving substrate adhesion andtransparency.

Herein, R⁵⁹ to R⁶³ each are hydrogen, fluorine or a fluorinated alkylgroup of 1 to 4 carbon atoms, and at least one of R⁶⁰ to R⁶³ contains atleast one fluorine atom. R⁶⁴ and R⁶⁵ each are hydrogen, methyl ortrifluoromethyl.

In the inventive polymers wherein U1 represents units of formula (2), U2represents units of formulae (3a) to (3f), U3 represents units offormulae (4), (4a) and (4b), U4 represents units of formulae (5), (5a)and (5b), U5 represents units of formula (6), and U6 represents adhesiveand transparent units other than the foregoing, and U1+U2+U3+U4+U5+U6=1,U's are preferably in the range:

-   0<U1≦0.9, more preferably 0.1≦U1≦0.5,-   0≦U2≦0.6, more preferably 0≦U2≦0.4,-   0≦U3≦0.6, more preferably 0≦U3≦0.4,-   0≦U4≦0.6, more preferably 0≦U4≦0.4,-   0≦U5≦0.7, more preferably 0≦U5≦0.5, and-   0≦U6≦0.4, more preferably 0≦U6≦0.2.

The polymers of the invention are generally synthesized by dissolvingmonomers corresponding to the respective units of formulae (2), (3a) to(3f), (4), (4a), (4b), (5), (5a), (5b) and (6) and optionally, anadhesion-improving monomer, a transparency-improving monomer and thelike in a solvent, adding a catalyst thereto, and effectingpolymerization reaction while heating or cooling the system ifnecessary. The polymerization reaction depends on the type of initiatoror catalyst, trigger means (including light, heat, radiation andplasma), and polymerization conditions (including temperature, pressure,concentration, solvent, and additives). Commonly used for preparation ofthe polymers of the invention are radical copolymerization of triggeringpolymerization with initiators such as 2,2′-azobisisobutyronitrile(AIBN) or the like, and ion (anion) polymerization using catalysts suchas alkyl lithium. These polymerization steps may be carried out in theirconventional manner.

The radical polymerization initiator used herein is not critical.Exemplary initiators include azo compounds such as AIBN,2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(2,4-dimethylvaleronitrile), and2,2′-azobis(2,4,4-trimethylpentane); peroxide compounds such astert-butyl peroxypivalate, lauroyl peroxide, benzoyl peroxide andtert-butyl peroxylaurate; water-soluble initiators, for example,persulfate salts such as potassium persulfate; and redox combinations ofpotassium persulfate or peroxides such as hydrogen peroxide withreducing agents such as sodium sulfite. The amount of the polymerizationinitiator used is determined as appropriate in accordance with suchfactors as the identity of initiator and polymerization conditions,although the amount is often in the range of about 0.001 to 5% byweight, especially about 0.01 to 2% by weight based on the total weightof monomers to be polymerized.

For the polymerization reaction, a solvent may be used. Thepolymerization solvent used herein is preferably one which does notinterfere with the polymerization reaction. Typical solvents includeester solvents such as ethyl acetate and n-butyl acetate, ketonesolvents such as acetone, methyl ethyl ketone and methyl isobutylketone, aliphatic or aromatic hydrocarbon solvents such as toluene,xylene and cyclohexane, alcohol solvents such as isopropyl alcohol andethylene glycol monomethyl ether, and ether solvents such as diethylether, dioxane, and tetrahydrofuran. These solvents may be used alone orin admixture of two or more. Further, any of well-known molecular weightmodifiers such as dodecylmercaptan may be used in the polymerizationsystem.

The temperature of polymerization reaction varies in accordance with theidentity of polymerization initiator and the boiling point of thesolvent although it is often preferably in the range of about 20 to 200°C., and especially about 50 to 140° C. Any desired reactor or vessel maybe used for the polymerization reaction.

From the solution or dispersion of the polymer thus obtained, theorganic solvent or water serving as the reaction medium is removed byany of well-known techniques. Suitable techniques include, for example,re-precipitation followed by filtration, and heat distillation undervacuum.

Desirably the polymer has a weight average molecular weight of about1,000 to about 500,000, and especially about 2,000 to about 100,000.

The polymer of the invention can be used as a base resin in resistcompositions, specifically chemical amplification type resistcompositions, and especially chemical amplification type positiveworking resist compositions. It is understood that the polymer of theinvention may be admixed with another polymer for the purpose ofaltering the dynamic properties, thermal properties, alkali solubilityand other physical properties of polymer film. The type of the otherpolymer which can be admixed is not critical. Any of polymers known tobe useful in resist use may be admixed in any desired proportion.

In the practice of the invention, the sulfonate compounds of the formula(1) can be prepared by the following scheme, although their preparationis not limited thereto.

Herein R¹ to R³ are as defined above.

The reaction readily takes place under well-known conditions.Preferably, the alcohol reactant and a base such as pyridine aresimultaneously added to a solvent such as dichloromethane, andchloroethanesulfonyl chloride is added dropwise under ice cooling. Thedesired monomer is obtained in this way.

Resist Composition

As long as the polymer of the invention is used as a base resin, theresist composition of the invention may be prepared using well-knowncomponents. In a preferred embodiment, the chemically amplified positiveresist composition is defined as comprising (A) the above-definedpolymer as a base resin, (B) an organic solvent, and (C) a photoacidgenerator. In the resist composition, there may be further formulated(D) a basic compound and/or (E) a dissolution inhibitor.

Component (B)

The organic solvent used as component (B) in the invention may be anyorganic solvent in which the base resin, photoacid generator, and othercomponents are soluble. Illustrative, non-limiting, examples of theorganic solvent include ketones such as cyclohexanone andmethyl-2-n-amylketone; alcohols such as 3-methoxybutanol,3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether,ethylene glycol monomethyl ether, propylene glycol monoethyl ether,ethylene glycol monoethyl ether, propylene glycol dimethyl ether, anddiethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate, propylene glycol monoethyl ether acetate,ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone.

Also useful are fluorinated organic solvents. Illustrative, non-limitingexamples include 2-fluoroanisole, 3-fluoroanisole, 4-fluoroanisole,2,3-difluoroanisole, 2,4-difluoroanisole, 2,5-difluoroanisole,5,8-difluoro-1,4-benzodioxane, 2,3-difluorobenzyl alcohol,1,3-difluoro-2-propanol, 2′,4′-difluoropropiophenone,2,4-difluorotoluene, trifluoroacetaldehyde ethyl hemiacetal,trifluoroacetamide, trifluoroethanol, 2,2,2-trifluorobutyrate,ethylheptafluoroethanol, ethyl heptafluorobutylacetate, ethylhexafluoroglutarylmethyl, ethyl 3-hydroxy-4,4,4-trifluoroacetoacetate,ethyl pentafluoropropynylacetate, ethyl perfluorooctanoate, ethyl4,4,4-trifluoroacetoacetate, ethyl 4,4,4-trifluorobutyrate, ethyl4,4,4-trifluorocrotonate, ethyl trifluoropyruvate, sec-ethyltrifluoroacetate, fluorocyclohexane,2,2,3,3,4,4,4-heptafluoro-1-butanol,1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione,1,1,1,3,5,5,5-heptafluoropentane-2,4-dione,3,3,4,4,5,5,5-heptafluoro-2-pentanol,3,3,4,4,5,5,5-heptafluoro-2-pentanone, isopropyl4,4,4-trifluoroacetoacetate, methyl perfluorodecanoate, methylperfluoro(2-methyl-3-oxahexanoate), methyl perfluorononanoate, methylperfluorooctanoate, methyl 2,3,3,3-tetrafluoropropionate, methyltrifluoroacetoacetate, 1,1,1,2,2,6,6,6-octafluoro-2,4-hexanedione,2,2,3,3,4,4,5,5-octafluoro-1-pentanol, 1H,1H,2H,2H-perfluoro-1-decanol,perfluoro-2,5-dimethyl-3,6-dioxane anionic acid methyl ester,2H-perfluoro-5-methyl-3,6-dioxanonane,1H,1H,2H,3H,3H-perfluorononane-1,2-diol, 1H,1H,9H-perfluoro-1-nonanol,1H,1H-perfluorooctanol, 1H,1H,2H,2H-perfluorooctanol,2H-perfluoro-5,8,11,14-tetramethyl-3,6,9,12,15-pentaoxaoctadecane,perfluorotributylamine, perfluorotrihexylamine,perfluoro-2,5,8-trimethyl-3,6,9,12,15-pentaoxaoctadecane,perfluorotributylamine, perfluorotrihexylamine, methylperfluoro-2,5,8-trimethyl-3,6,9-trioxadodecanoate,perfluorotripentylamine, perfluorotriisopropylamine,1H,1H,2H,3H,3H-perfluoroundecane-1,2-diol, trifluorobutanol,1,1,1-trifluoro-5-methyl-2,4-hexanedione, 1,1,1-trifluoro-2-propanol,3,3,3-trifluoro-1-propanol, 1,1,1-trifluoro-2-propyl acetate,perfluorobutyltetrahydrofuran, perfluorodecalin,perfluoro(1,2-dimethylcyclohexane), perfluoro(1,3-dimethylcyclohexane),propylene glycol trifluoromethyl ether acetate, propylene glycol methylether trifluoromethyl acetate, butyl trifluoromethylacetate, methyl3-trifluoromethoxypropionate, perfluorocyclohexane, propylene glycoltrifluoromethyl ether, butyl trifluoroacetate, and1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione.

These solvents may be used alone or in combinations of two or morethereof. Of the above organic solvents, preferred are diethylene glycoldimethyl ether and 1-ethoxy-2-propanol, in which the photoacid generatoris most soluble, and propylene glycol monomethyl ether acetate which issafe, and mixtures thereof.

The solvent is preferably used in an amount of about 300 to 10,000 partsby weight, more preferably about 500 to 5,000 parts by weight per 100parts by weight of the base resin.

Component (C)

The photoacid generator is a compound capable of generating an acid uponexposure to high energy radiation or electron beams and includes thefollowing:

-   (i) onium salts of the formula (P1a-1), (P1a-2) or (P1b),-   (ii) diazomethane derivatives of the formula (P2),-   (iii) glyoxime derivatives of the formula (P3),-   (iv) bissulfone derivatives of the formula (P4),-   (v) sulfonic acid esters of N-hydroxyimide compounds of the formula    (P5),-   (vi) β-ketosulfonic acid derivatives,-   (vii) disulfone derivatives,-   (viii) nitrobenzylsulfonate derivatives, and-   (ix) sulfonate derivatives.

These photoacid generators are described in detail.

(i) Onium Salts of Formula (P1a-1), (P1a-2) or (P1b):

Herein, R^(101a), R^(101b), and R^(101c) independently representstraight, branched or cyclic alkyl, alkenyl, oxoalkyl or oxoalkenylgroups of 1 to 12 carbon atoms, aryl groups of 6 to 20 carbon atoms, oraralkyl or aryloxoalkyl groups of 7 to 12 carbon atoms, wherein some orall of the hydrogen atoms may be replaced by alkoxy or other groups.Also, R^(101b) and R^(101c), taken together, may form a ring. R^(101b)and R^(101c) each are alkylene groups of 1 to 6 carbon atoms when theyform a ring. K⁻ is a non-nucleophilic counter ion.

R^(101a), R^(101b), and R^(101c) may be the same or different and areillustrated below. Exemplary alkyl groups include methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl,cyclopentyl, cyclohexyl, cycloheptyl, cyclopropylmethyl,4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl.Exemplary alkenyl groups include vinyl, allyl, propenyl, butenyl,hexenyl, and cyclohexenyl. Exemplary oxoalkyl groups include2-oxocyclopentyl and 2-oxocyclohexyl as well as 2-oxopropyl,2-cyclopentyl-2-oxoethyl, 2-cyclohexyl-2-oxoethyl, and2-(4-methylcyclohexyl)-2-oxoethyl. Exemplary aryl groups include phenyland naphthyl; alkoxyphenyl groups such as p-methoxyphenyl,m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl; alkylnaphthyl groups such asmethylnaphthyl and ethylnaphthyl; alkoxynaphthyl groups such asmethoxynaphthyl and ethoxynaphthyl; dialkylnaphthyl groups such asdimethylnaphthyl and diethylnaphthyl; and dialkoxynaphthyl groups suchas dimethoxynaphthyl and diethoxynaphthyl. Exemplary aralkyl groupsinclude benzyl, phenylethyl, and phenethyl. Exemplary aryloxoalkylgroups are 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl,2-(1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl. Examples ofthe non-nucleophilic counter ion represented by K⁻ include halide ionssuch as chloride and bromide ions, fluoroalkylsulfonate ions such astriflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate,arylsulfonate ions such as tosylate, benzenesulfonate,4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, andalkylsulfonate ions such as mesylate and butanesulfonate.

Herein, R^(102a) and R^(102b) independently represent straight, branchedor cyclic alkyl groups of 1 to 8 carbon atoms. R¹⁰³ represents astraight, branched or cyclic alkylene group of 1 to 10 carbon atoms.R^(104a) and R^(104b) independently represent 2-oxoalkyl groups of 3 to7 carbon atoms. K⁻ is a non-nucleophilic counter ion.

Illustrative of the groups represented by R^(102a) and R^(102b) aremethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl,cyclopropylmethyl, 4-methylcyclohexyl, and cyclohexylmethyl.Illustrative of the groups represented by R¹⁰³ are methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene,1,4-cyclohexylene, 1,2-cyclohexylene, 1,3-cyclopentylene,1,4-cyclooctylene, and 1,4-cyclohexanedimethylene. Illustrative of thegroups represented by R^(104a) and R^(104b) are 2-oxopropyl,2-oxocyclopentyl, 2-oxocyclohexyl, and 2-oxocycloheptyl. Illustrativeexamples of the counter ion represented by K⁻ are the same asexemplified for formulae (P1a-1) and (P1a-2).

(ii) Diazomethane Derivatives of Formula (P2)

Herein, R¹⁰⁵ and R¹⁰⁶ independently represent straight, branched orcyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms, arylor halogenated aryl groups of 6 to 20 carbon atoms, or aralkyl groups of7 to 12 carbon atoms.

Of the groups represented by R¹⁰⁵ and R¹⁰⁶, exemplary alkyl groupsinclude methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl, octyl, amyl, cyclopentyl, cyclohexyl,cycloheptyl, norbornyl, and adamantyl. Exemplary halogenated alkylgroups include trifluoromethyl, 1,1,1-trifluoroethyl,1,1,1-trichloroethyl, and nonafluorobutyl. Exemplary aryl groups includephenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl,o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groupsinclude fluorophenyl, chlorophenyl, and 1,2,3,4,5-pentafluorophenyl.Exemplary aralkyl groups include benzyl and phenethyl.

(iii) Glyoxime Derivatives of Formula (P3)

Herein, R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ independently represent straight, branchedor cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms,aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkylgroups of 7 to 12 carbon atoms. Also, R¹⁰⁸ and R¹⁰⁹, taken together, mayform a ring. R¹⁰⁸ and R¹⁰⁹ each are straight or branched alkylene groupsof 1 to 6 carbon atoms when they form a ring.

Illustrative examples of the alkyl, halogenated alkyl, aryl, halogenatedaryl, and aralkyl groups represented by R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ are thesame as exemplified for R¹⁰⁵ and R¹⁰⁶. Examples of the alkylene groupsrepresented by R¹⁰⁸ and R¹⁰⁹ include methylene, ethylene, propylene,butylene, and hexylene.

(iv) Bissulfone Derivatives of Formula (P4)

Herein, R^(101a) and R^(101b) are as defined above.

(v) Sulfonic Acid Esters of N-hydroxyimide Compounds of Formula (P5)

Herein, R¹¹⁰ is an arylene group of 6 to 10 carbon atoms, alkylene groupof 1 to 6 carbon atoms, or alkenylene group of 2 to 6 carbon atomswherein some or all of the hydrogen atoms may be replaced by straight orbranched alkyl or alkoxy groups of 1 to 4 carbon atoms, nitro, acetyl,or phenyl groups. R¹¹¹ is a straight, branched or cyclic alkyl group of1 to 8 carbon atoms, alkenyl, alkoxyalkyl, phenyl or naphthyl groupwherein some or all of the hydrogen atoms may be replaced by alkyl oralkoxy groups of 1 to 4 carbon atoms, phenyl groups (which may havesubstituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms, nitro, oracetyl group), hetero-aromatic groups of 3 to 5 carbon atoms, orchlorine or fluorine atoms.

Of the groups represented by R¹¹⁰, exemplary arylene groups include1,2-phenylene and 1,8-naphthylene; exemplary alkylene groups includemethylene, ethylene, trimethylene, tetramethylene, phenylethylene, andnorbornane-2,3-diyl; and exemplary alkenylene groups include1,2-vinylene, 1-phenyl-1,2-vinylene, and 5-norbornene-2,3-diyl. Of thegroups represented by R¹¹¹, exemplary alkyl groups are as exemplifiedfor R^(101a) to R^(101c); exemplary alkenyl groups include vinyl,1-propenyl, allyl, 1-butenyl, 3-butenyl, isoprenyl, 1-pentenyl,3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl, 3-hexenyl, 5-hexenyl,1-heptenyl, 3-heptenyl, 6-heptenyl, and 7-octenyl; and exemplaryalkoxyalkyl groups include methoxymethyl, ethoxymethyl, propoxymethyl,butoxymethyl, pentyloxymethyl, hexyloxymethyl, heptyloxymethyl,methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl, pentyloxyethyl,hexyloxyethyl, methoxypropyl, ethoxypropyl, propoxypropyl, butoxypropyl,methoxybutyl, ethoxybutyl, propoxybutyl, methoxypentyl, ethoxypentyl,methoxyhexyl, and methoxyheptyl.

Of the substituents on these groups, the alkyl groups of 1 to 4 carbonatoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl andtert-butyl; the alkoxy groups of 1 to 4 carbon atoms include methoxy,ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, and tert-butoxy; thephenyl groups which may have substituted thereon an alkyl or alkoxy of 1to 4 carbon atoms, nitro, or acetyl group include phenyl, tolyl,p-tert-butoxyphenyl, p-acetylphenyl and p-nitrophenyl; thehetero-aromatic groups of 3 to 5 carbon atoms include pyridyl and furyl.

Illustrative examples of the photoacid generator include:

onium salts such as

-   diphenyliodonium trifluoromethanesulfonate,-   (p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate,-   diphenyliodonium p-toluenesulfonate,-   (p-tert-butoxyphenyl)phenyliodonium p-toluenesulfonate,-   triphenylsulfonium trifluoromethanesulfonate,-   (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,-   bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethanesulfonate,-   tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,-   triphenylsulfonium p-toluenesulfonate,    (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,-   bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate,-   tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,-   triphenylsulfonium nonafluorobutanesulfonate,-   triphenylsulfonium butanesulfonate,-   trimethylsulfonium trifluoromethanesulfonate,-   trimethylsulfonium p-toluenesulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium    trifluoromethanesulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate,-   dimethylphenylsulfonium trifluoromethanesulfonate,-   dimethylphenylsulfonium p-toluenesulfonate,-   dicyclohexylphenylsulfonium trifluoromethanesulfonate,-   dicyclohexylphenylsulfonium p-toluenesulfonate,-   trinaphthylsulfonium trifluoromethanesulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium    trifluoromethanesulfonate,-   (2-norbornyl)methyl(2-oxocyclohexyl)sulfonium    trifluoromethanesulfonate,-   ethylenebis[methyl(2-oxocyclopentyl)sulfonium    trifluoromethanesulfonate], and-   1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;

diazomethane derivatives such as

-   bis(benzenesulfonyl)diazomethane,-   bis(p-toluenesulfonyl)diazomethane,-   bis(xylenesulfonyl)diazomethane,-   bis(cyclohexylsulfonyl)diazomethane,-   bis(cyclopentylsulfonyl)diazomethane,-   bis(n-butylsulfonyl)diazomethane,-   bis(isobutylsulfonyl)diazomethane,-   bis(sec-butylsulfonyl)diazomethane,-   bis(n-propylsulfonyl)diazomethane,-   bis(isopropylsulfonyl)diazomethane,-   bis(tert-butylsulfonyl)diazomethane,-   bis(n-amylsulfonyl)diazomethane,-   bis(isoamylsulfonyl)diazomethane,-   bis(sec-amylsulfonyl)diazomethane,-   bis(tert-amylsulfonyl)diazomethane,-   1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane,-   1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and-   1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane;

glyoxime derivatives such as

-   bis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,-   bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,-   bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,-   bis-O-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,-   bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,-   bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,-   bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,-   bis-O-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,-   bis-O-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,-   bis-O-(methanesulfonyl)-α-dimethylglyoxime,-   bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,-   bis-O-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime,-   bis-O-(tert-butanesulfonyl)-α-dimethylglyoxime,-   bis-O-(perfluorooctanesulfonyl)-α-dimethylglyoxime,-   bis-O-(cyclohexanesulfonyl)-α-dimethylglyoxime,-   bis-O-(benzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(xylenesulfonyl)-α-dimethylglyoxime, and-   bis-O-(camphorsulfonyl)-α-dimethylglyoxime;

bissulfone derivatives such as

-   bisnaphthylsulfonylmethane, bistrifluoromethylsulfonylmethane,-   bismethylsulfonylmethane, bisethylsulfonylmethane,-   bispropylsulfonylmethane, bisisopropylsulfonylmethane,-   bis-p-toluenesulfonylmethane, and bisbenzenesulfonylmethane;

β-ketosulfone derivatives such as

-   2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and-   2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane;

nitrobenzyl sulfonate derivatives such as

-   2,6-dinitrobenzyl p-toluenesulfonate and-   2,4-dinitrobenzyl p-toluenesulfonate;

sulfonic acid ester derivatives such as

-   1,2,3-tris(methanesulfonyloxy)benzene,-   1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and-   1,2,3-tris(p-toluenesulfonyloxy)benzene; and

sulfonic acid esters of N-hydroxyimides such as

-   N-hydroxysuccinimide methanesulfonate,-   N-hydroxysuccinimide trifluoromethanesulfonate,-   N-hydroxysuccinimide ethanesulfonate,-   N-hydroxysuccinimide 1-propanesulfonate,-   N-hydroxysuccinimide 2-propanesulfonate,-   N-hydroxysuccinimide 1-pentanesulfonate,-   N-hydroxysuccinimide 1-octanesulfonate,-   N-hydroxysuccinimide p-toluenesulfonate,-   N-hydroxysuccinimide p-methoxybenzenesulfonate,-   N-hydroxysuccinimide 2-chloroethanesulfonate,-   N-hydroxysuccinimide benzenesulfonate,-   N-hydroxysuccinimide 2,4,6-trimethylbenzenesulfonate,-   N-hydroxysuccinimide 1-naphthalenesulfonate,-   N-hydroxysuccinimide 2-naphthalenesulfonate,-   N-hydroxy-2-phenylsuccinimide methanesulfonate,-   N-hydroxymaleimide methanesulfonate,-   N-hydroxymaleimide ethanesulfonate,-   N-hydroxy-2-phenylmaleimide methanesulfonate,-   N-hydroxyglutarimide methanesulfonate,-   N-hydroxyglutarimide benzenesulfonate,-   N-hydroxyphthalimide methanesulfonate,-   N-hydroxyphthalimide benzenesulfonate,-   N-hydroxyphthalimide trifluoromethanesulfonate,-   N-hydroxyphthalimide p-toluenesulfonate,-   N-hydroxynaphthalimide methanesulfonate,-   N-hydroxynaphthalimide benzenesulfonate,-   N-hydroxy-5-norbornene-2,3-dicarboxyimide methanesulfonate,-   N-hydroxy-5-norbornene-2,3-dicarboxyimide trifluoromethanesulfonate,    and-   N-hydroxy-5-norbornene-2,3-dicarboxyimide p-toluenesulfonate.

Preferred among these photoacid generators are onium salts such astriphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,

-   tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,-   triphenylsulfonium p-toluenesulfonate,-   (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,-   tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,-   trinaphthylsulfonium trifluoromethanesulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium    trifluoromethanesulfonate,-   (2-norbornyl)methyl(2-oxocylohexyl)sulfonium    trifluoromethanesulfonate, and-   1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;    diazomethane derivatives such as-   bis(benzenesulfonyl)diazomethane,-   bis(p-toluenesulfonyl)diazomethane,-   bis(cyclohexylsulfonyl)diazomethane,-   bis(n-butylsulfonyl)diazomethane,-   bis(isobutylsulfonyl)diazomethane,-   bis(sec-butylsulfonyl)diazomethane,-   bis(n-propylsulfonyl)diazomethane,-   bis(isopropylsulfonyl)diazomethane, and-   bis(tert-butylsulfonyl)diazomethane;    glyoxime derivatives such as-   bis-O-(p-toluenesulfonyl)-α-dimethylglyoxime and-   bis-O-(n-butanesulfonyl)-α-dimethylglyoxime;    bissulfone derivatives such as-   bisnaphthylsulfonylmethane; and sulfonic acid esters of    N-hydroxyimide compounds such as-   N-hydroxysuccinimide methanesulfonate,-   N-hydroxysuccinimide trifluoromethanesulfonate,-   N-hydroxysuccinimide 1-propanesulfonate,-   N-hydroxysuccinimide 2-propanesulfonate,-   N-hydroxysuccinimide 1-pentanesulfonate,-   N-hydroxysuccinimide p-toluenesulfonate,-   N-hydroxynaphthalimide methanesulfonate, and-   N-hydroxynaphthalimide benzenesulfonate.

These photoacid generators may be used singly or in combinations of twoor more thereof. Onium salts are effective for improving rectangularity,while diazomethane derivatives and glyoxime derivatives are effectivefor reducing standing waves. The combination of an onium salt with adiazomethane or a glyoxime derivative allows for fine adjustment of theprofile.

The photoacid generator is added in an amount of 0.1 to 50 parts, andespecially 0.5 to 40 parts by weight, per 100 parts by weight of thebase resin (all parts are by weight, hereinafter). Less than 0.1 part ofthe photoacid generator may generate a less amount of acid uponexposure, sometimes leading to a poor sensitivity and resolution whereasmore than 50 parts of the photoacid generator may adversely affecttransmittance and resolution.

Component (D)

The basic compound used as component (D) is preferably a compoundcapable of suppressing the rate of diffusion when the acid generated bythe photoacid generator diffuses within the resist film. The inclusionof this type of basic compound holds down the rate of acid diffusionwithin the resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure, thus reducingsubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

Examples of suitable basic compounds include primary, secondary, andtertiary aliphatic amines, mixed amines, aromatic amines, heterocyclicamines, carboxyl group-bearing nitrogenous compounds, sulfonylgroup-bearing nitrogenous compounds, hydroxyl group-bearing nitrogenouscompounds, hydroxyphenyl group-bearing nitrogenous compounds, alcoholicnitrogenous compounds, amide derivatives, and imide derivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,iso-butylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine,di-iso-propylamine, di-n-butylamine, di-iso-butylamine,di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine,dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine,tri-iso-butylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic amines includeaniline derivatives (e.g., aniline, N-methylaniline, N-ethylaniline,N-propylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline,4-methylaniline, ethylaniline, propylaniline, trimethylaniline,2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline,2,6-dinitroaniline, 3,5-dinitroaniline, and N,N-dimethyltoluidine),diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine,phenylenediamine, naphthylamine, and diaminonaphthalene. Examples ofsuitable heterocyclic amines include pyrrole derivatives (e.g., pyrrole,2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole,and N-methylpyrrole), oxazole derivatives (e.g., oxazole andisooxazole), thiazole derivatives (e.g., thiazole and isothiazole),imidazole derivatives (e.g., imidazole, 4-methylimidazole, and4-methyl-2-phenylimidazole), pyrazole derivatives, furazan derivatives,pyrroline derivatives (e.g., pyrroline and 2-methyl-1-pyrroline),pyrrolidine derivatives (e.g., pyrrolidine, N-methylpyrrolidine,pyrrolidinone, and N-methylpyrrolidone), imidazoline derivatives,imidazolidine derivatives, pyridine derivatives (e.g., pyridine,methylpyridine, ethylpyridine, propylpyridine, butylpyridine,4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine,triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine,4-tert-butylpyridine, diphenylpyridine, benzylpyridine, methoxypyridine,butoxypyridine, dimethoxypyridine, 1-methyl-2-pyridone,4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable carboxyl group-bearing nitrogenous compoundsinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g., nicotinic acid, alanine, arginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine).

Examples of suitable sulfonyl group-bearing nitrogenous compoundsinclude 3-pyridinesulfonic acid and pyridinium p-toluenesulfonate.

Examples of suitable hydroxyl group-bearing nitrogenous compounds,hydroxyphenyl group-bearing nitrogenous compounds, and alcoholicnitrogenous compounds include 2-hydroxypyridine, aminocresol,2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine,diethanolamine, triethanolamine, N-ethyldiethanolamine,N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol,2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol,4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine,1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine,piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine,1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol,3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol,3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol,N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide.

Examples of suitable amide derivatives include formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, and benzamide. Suitable imidederivatives include phthalimide, succinimide, and maleimide.

In addition, basic compounds of the following general formula (B)-1 mayalso be included alone or in admixture.

In the formulas, n is 1, 2 or 3. The side chain X may be the same ordifferent and is represented by the formula (X)-1, (X)-2 or (X)-3. Theside chain Y may be the same or different and stands for hydrogen or astraight, branched or cyclic alkyl group of 1 to 20 carbon atoms whichmay contain an ether or hydroxyl group. Two or three X's may bondtogether to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched alkylene groups of 1 to 4 carbon atoms; R³⁰¹ and R³⁰⁴ areindependently hydrogen, straight, branched or cyclic alkyl groups of 1to 20 carbon atoms, which may contain at least one hydroxyl group,ether, ester or lactone ring; and R³⁰³ is a single bond or a straight orbranched alkylene group of 1 to 4 carbon atoms; and R³⁰⁶ is a straight,branched or cyclic alkyl group of 1 to 20 carbon atoms, which maycontain at least one hydroxyl group, ether, ester or lactone ring.

Illustrative, non-limiting examples of the compounds of formula (B)-1include tris(2-methoxymethoxyethyl)amine,tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

Also useful are one or more of cyclic structure-bearing basic compoundshaving the following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branchedalkylene group of 2 to 20 carbon atoms which may contain one or morecarbonyl, ether, ester or sulfide groups.

Illustrative examples of the cyclic structure-bearing basic compoundshaving formula (B)-2 include 1-[2-(methoxymethoxy)ethyl]pyrrolidine,1-[2-(methoxymethoxy)ethyl]piperidine,4-[2-(methoxymethoxy)ethyl]morpholine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethylacetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate,2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate,2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethylmethoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine,1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate,methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate,2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,tetrahydrofurfuryl 3-morpholinopropionate, glycidyl3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate,2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl3-morpholinopropionate, cyclohexyl 3-piperidinopropionate,α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone,β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methylpiperidinoacetate, methyl morpholinoacetate, methylthiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, and 2-methoxyethylmorpholinoacetate.

Also, one or more of cyano-bearing basic compounds having the followinggeneral formulae (B)-3 to (B)-6 may be blended.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ each areindependently a straight or branched alkylene group of 1 to 4 carbonatoms.

Illustrative examples of the cyano-bearing basic compounds include3-(diethylamino)propiononitrile,N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methylN-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methylN-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile,N,N-bis(2-hydroxyethyl)aminoacetonitrile,N,N-bis(2-acetoxyethyl)aminoacetonitrile,N,N-bis(2-formyloxyethyl)aminoacetonitrile,N,N-bis(2-methoxyethyl)aminoacetonitrile,N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methylN-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methylN-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile,1-piperidinepropiononitrile, 4-morpholinepropiononitrile,1-pyrrolidineacetonitrile, 1-piperidineacetonitrile,4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate,cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl3-diethylaminopropionate, 2-cyanoethylN,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate,2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl4-morpholinepropionate.

These basic compounds may be used alone or in admixture of any. Thebasic compound is preferably formulated in an amount of 0.001 to 2parts, and especially 0.01 to 1 part by weight, per 100 parts by weightof the base resin. Less than 0.001 part of the basic compound may failto achieve the desired effects thereof, while the use of more than 2parts would result in too low a sensitivity.

Component (E)

The dissolution inhibitor (E) is preferably selected from compoundspossessing a weight average molecular weight of 100 to 1,000 and havingon the molecule at least two phenolic hydroxyl groups, in which anaverage of from 10 to 100 mol % of all the hydrogen atoms on thephenolic hydroxyl groups are replaced with acid labile groups.

Illustrative, non-limiting, examples of the dissolution inhibitor (E)which are useful herein include

-   bis(4-(2′-tetrahydropyranyloxy)phenyl)methane,-   bis(4-(2′-tetrahydrofuranyloxy)phenyl)methane,-   bis(4-tert-butoxyphenyl)methane,-   bis(4-tert-butoxycarbonyloxyphenyl)methane,-   bis(4-tert-butoxycarbonylmethyloxyphenyl)methane,-   bis(4-(1′-ethoxyethoxy)phenyl)methane,-   bis(4-(1′-ethoxypropyloxy)phenyl)methane,-   2,2-bis(4′-(2″-tetrahydropyranyloxy))propane,-   2,2-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)propane,-   2,2-bis(4′-tert-butoxyphenyl)propane,-   2,2-bis(4′-tert-butoxycarbonyloxyphenyl)propane,-   2,2-bis(4-tert-butoxycarbonylmethyloxyphenyl)propane,-   2,2-bis(4′-(1″-ethoxyethoxy)phenyl)propane,-   2,2-bis(4′-(1″-ethoxypropyloxy)phenyl)propane,-   tert-butyl 4,4-bis(4′-(2″-tetrahydropyranyloxy)phenyl)valerate,-   tert-butyl 4,4-bis(4′-(2″-tetrahydrofuranyloxy)phenyl)valerate,-   tert-butyl 4,4-bis(4′-tert-butoxyphenyl)valerate,-   tert-butyl 4,4-bis(4-tert-butoxycarbonyloxyphenyl)valerate,-   tert-butyl 4,4-bis(4′-tert-butoxycarbonylmethyloxyphenyl)valerate,-   tert-butyl 4,4-bis(4′-(1″-ethoxyethoxy)phenyl)valerate,-   tert-butyl 4,4-bis(4′-(1″-ethoxypropyloxy)phenyl)valerate,-   tris(4-(2′-tetrahydropyranyloxy)phenyl)methane,-   tris(4-(2′-tetrahydrofuranyloxy)phenyl)methane,-   tris(4-tert-butoxyphenyl)methane,-   tris(4-tert-butoxycarbonyloxyphenyl)methane,-   tris(4-tert-butoxycarbonyloxymethylphenyl)methane,-   tris(4-(1′-ethoxyethoxy)phenyl)methane,-   tris(4-(1′-ethoxypropyloxy)phenyl)methane,-   1,1,2-tris(4′-(2″-tetrahydropyranyloxy)phenyl)ethane,-   1,1,2-tris(4′-(2″-tetrahydrofuranyloxy)phenyl)ethane,-   1,1,2-tris(4′-tert-butoxyphenyl)ethane,-   1,1,2-tris(4′-tert-butoxycarbonyloxyphenyl)ethane,-   1,1,2-tris(4′-tert-butoxycarbonylmethyloxyphenyl)ethane,-   1,1,2-tris(4′-(1′-ethoxyethoxy)phenyl)ethane, and-   1,1,2-tris(4′-(1′-ethoxypropyloxy)phenyl)ethane.

The compounds serving as dissolution inhibitor have a weight averagemolecular weight of 100 to 1,000, preferably 150 to 800.

An appropriate amount of the dissolution inhibitor (E) is 0 to about 50parts, preferably about 5 to 50 parts, and especially about 10 to 30parts by weight per 100 parts by weight of the base resin. Less amountsof the dissolution inhibitor may fail to yield an improved resolution,whereas too much amounts would lead to slimming of the patterned film,and thus a decline in resolution. The inhibitor may be used singly or asa mixture of two or more thereof.

The resist composition of the invention may include optionalingredients, typically a surfactant which is commonly used for improvingthe coating characteristics. Optional ingredients may be added inconventional amounts so long as this does not compromise the objects ofthe invention.

Illustrative, non-limiting, examples of the surfactant include nonionicsurfactants, for example, polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenolether and polyoxyethylene nonylphenol ether, polyoxyethylenepolyoxypropylene block copolymers, sorbitan fatty acid esters such assorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate,and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantrioleate, and polyoxyethylene sorbitan tristearate; fluorochemicalsurfactants such as EFTOP EF301, EF303 and EF352 (Tohkem Products Co.,Ltd.), Megaface F171, F172 and F173 (Dai-Nippon Ink & Chemicals, Inc.),Fluorad FC430 and FC431 (Sumitomo 3M Co., Ltd.), Asahiguard AG710,Surflon S-381, S-382, SC101, SC102, SC103, SC104, SC105, SC106, SurfynolE1004, KH-10, KH-20, KH-30 and KH-40 (Asahi Glass Co., Ltd.);organosiloxane polymers KP341, X-70-092 and X-70-093 (Shin-Etsu ChemicalCo., Ltd.), acrylic acid or methacrylic acid Polyflow No. 75 and No. 95(Kyoeisha Ushi Kagaku Kogyo Co., Ltd.). Inter alia, FC430, SurflonS-381, Surfynol E1004, KH-20 and KH-30 are preferred. These surfactantsmay be used alone or in admixture.

Pattern formation using the resist composition of the invention may becarried out by a known lithographic technique. For example, the resistcomposition may be applied onto a substrate such as a silicon wafer byspin coating or the like to form a resist film having a thickness of 0.1to 1.0 μm, which is then pre-baked on a hot plate at 60 to 200° C. for10 seconds to 10 minutes, and preferably at 80 to 150° C. for ½ to 5minutes. A patterning mask having the desired pattern may then be placedover the resist film, and the film exposed through the mask to anelectron beam or to high-energy radiation such as deep-UV rays, excimerlaser beams, or x-rays in a dose of about 1 to 200 mJ/cm², andpreferably about 10 to 100 mJ/cm², then post-exposure baked (PEB) on ahot plate at 60 to 150° C. for 10 seconds to 5 minutes, and preferablyat 80 to 130° C. for ½ to 3 minutes. Finally, development may be carriedout using as the developer an aqueous alkali solution, such as 0.1 to5%, and preferably 2 to 3%, tetramethylammonium hydroxide (TMAH), thisbeing done by a conventional method such as dipping, puddling, orspraying for a period of 10 seconds to 3 minutes, and preferably 30seconds to 2 minutes. These steps result in the formation of the desiredpattern on the substrate.

Of the various types of high-energy radiation that may be used, theresist composition of the invention is best suited to micro-patternformation with, in particular, deep-UV rays having a wavelength of 254to 120 nm, an excimer laser, especially ArF laser (193 nm), F₂ laser(157 nm), Kr₂ laser (146 nm), KrAr laser (134 nm) or Ar₂ laser (126 nm),x-rays, or an electron beam. Recommended is exposure to high-energyradiation in a wavelength band of 100 to 180 nm or 1 to 30 nm,specifically F₂ laser beam, Ar₂ laser beam or soft x-ray. The desiredpattern may not be obtainable outside the upper and lower limits of theabove range.

The resist composition of the invention is sensitive to high-energyradiation, maintains high transparency at a wavelength of up to 200 nm,and has improved alkali dissolution contrast and plasma etchingresistance. These features permit the inventive resist composition toeasily form a finely defined pattern having sidewalls perpendicular tothe substrate and a high aspect ratio through F₂ laser exposure, makingthe resist ideal as a micropatterning material in VLSI fabrication.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. The abbreviations used herein are AIBN for2,2′-azobisisobutyronitrile, GPC for gel permeation chromatography, NMRfor nuclear magnetic resonance, Mw for weight average molecular weight,Mn for number average molecular weight, Mw/Mn for molecular weightdistribution or dispersity, THF for tetrahydrofuran, and PGMEA forpropylene glycol monomethyl ether acetate.

Monomer Synthesis Example 1

Synthesis of Monomer 1

Into a flask were admitted 40 g of dichloromethane, 10.0 g of Alcohol 1shown below, and 13.0 g of pyridine. While the flask was immersed in anice bath to keep the internal temperature below 10° C., 13.36 g ofchloroethanesulfonyl chloride was added dropwise to the flask from adropping funnel. The dropwise addition was followed by 2 hours ofstirring. Conventional post treatment was carried out. The resultingoily matter was purified by silica gel chromatography, obtaining 10.9 gof Monomer 1. The yield was 64%.

Monomer Synthesis Example 2

Synthesis of Monomer 2

Into a flask were admitted 40 g of dichloromethane, 10.0 g of Alcohol 2shown below, and 10.8 g of pyridine. While the flask was immersed in anice bath to keep the internal temperature below 10° C., 11.11 g ofchloroethanesulfonyl chloride was added dropwise to the flask from adropping funnel. The dropwise addition was followed by 2 hours ofstirring. Conventional post treatment was carried out. The resultingoily matter was purified by silica gel chromatography, obtaining 11.4 gof Monomer 2. The yield was 72%.

Polymer Synthesis Example 1

Copolymerization of Monomer 1, Monomer 3 and Monomer 4 (0.4:0.2:0.4)

A 300-ml flask was charged with 5.47 g of Monomer 1, 6.55 g of Monomer3, shown below, and 7.98 g of Monomer 4, shown below, which weredissolved in 5.0 g of 1,4-dioxane. The system was fully purged ofoxygen, charged with 0.51 g of the initiator AIBN, and heated at 65° C.at which polymerization reaction took place for 24 hours.

The polymer thus obtained was worked up by pouring the reaction mixtureinto 1 liter of hexane whereupon the polymer precipitated. The procedureof dissolving the polymer in THF and pouring in 1 liter of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 12.5 g of a white polymer, which was foundto have a Mw of 6,100 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of respective unitsderived from Monomer 1, Monomer 3 and Monomer 4 in a molar ratio of0.37:0.19:0.44.

Polymer Synthesis Example 2

Copolymerization of Monomer 1, Monomer 5 and Monomer 6 (0.3:0.3:0.4)

A 300-ml flask was charged with 5.60 g of Monomer 1, 5.03 g of Monomer5, shown below, and 9.37 g of Monomer 6, shown below, which weredissolved in 5.0 g of 1,4-dioxane. The system was fully purged ofoxygen, charged with 0.70 g of the initiator AIBN, and heated at 65° C.at which polymerization reaction took place for 24 hours.

The polymer thus obtained was worked up by pouring the reaction mixtureinto 1 liter of hexane whereupon the polymer precipitated. The procedureof dissolving the polymer in THF and pouring in 1 liter of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 11.7 g of a white polymer, which was foundto have a Mw of 6,800 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of respective unitsderived from Monomer 1, Monomer 5 and Monomer 6 in a molar ratio of0.29:0.31:0.40.

Polymer Synthesis Example 3

Copolymerization of Monomer 1, Monomer 5 and Monomer 7 (0.3:0.3:0.4)

A 300-ml flask was charged with 4.38 g of Monomer 1, 3.94 g of Monomer 5and 11.7 g of Monomer 7, shown below, which were dissolved in 5.0 g of1,4-dioxane. The system was fully purged of oxygen, charged with 0.55 gof the initiator AIBN, and heated at 65° C. at which polymerizationreaction took place for 24 hours.

The polymer thus obtained was worked up by pouring the reaction mixtureinto 1 liter of hexane whereupon the polymer precipitated. The procedureof dissolving the polymer in THF and pouring in 1 liter of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 12.9 g of a white polymer, which was foundto have a Mw of 9,800 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of respective unitsderived from Monomer 1, Monomer 5 and Monomer 7 in a molar ratio of0.30:0.31:0.39.

Polymer Synthesis Example 4

Copolymerization of Monomer 2, Monomer 3 and Monomer 4 (0.4:0.2:0.4)

A 300-ml flask was charged with 5.93 g of Monomer 2, 6.34 g of Monomer 3and 7.73 g of Monomer 4, which were dissolved in 5.0 g of 1,4-dioxane.The system was fully purged of oxygen, charged with 0.50 g of theinitiator AIBN, and heated at 65° C. at which polymerization reactiontook place for 24 hours.

The polymer thus obtained was worked up by pouring the reaction mixtureinto 1 liter of hexane whereupon the polymer precipitated. The procedureof dissolving the polymer in THF and pouring in 1 liter of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 13.9 g of a white polymer, which was foundto have a Mw of 6,800 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of respective unitsderived from Monomer 2, Monomer 3 and Monomer 4 in a molar ratio of0.36:0.19:0.45.

Polymer Synthesis Example 5

Copolymerization of Monomer 2, Monomer 5 and Monomer 6 (0.3:0.3:0.4)

A 300-ml flask was charged with 6.06 g of Monomer 2, 4.87 g of Monomer 5and 9.07 g of Monomer 6, which were dissolved in 5.0 g of 1,4-dioxane.The system was fully purged of oxygen, charged with 0.68 g of theinitiator AIBN, and heated at 65° C. at which polymerization reactiontook place for 24 hours.

The polymer thus obtained was worked up by pouring the reaction mixtureinto 1 liter of hexane whereupon the polymer precipitated. The procedureof dissolving the polymer in THF and pouring in 1 liter of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 14.2 g of a white polymer, which was foundto have a Mw of 6,900 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of respective unitsderived from Monomer 2, Monomer 5 and Monomer 6 in a molar ratio of0.28:0.32:0.40.

Polymer Synthesis Example 6

Copolymerization of Monomer 2, Monomer 5 and Monomer 7 (0.3:0.3:0.4)

A 300-ml flask was charged with 4.78 g of Monomer 2, 3.84 g of Monomer 5and 11.38 g of Monomer 7, which were dissolved in 5.0 g of 1,4-dioxane.The system was fully purged of oxygen, charged with 0.54 g of theinitiator AIBN, and heated at 65° C. at which polymerization reactiontook place for 24 hours.

The polymer thus obtained was worked up by pouring the reaction mixtureinto 1 liter of hexane whereupon the polymer precipitated. The procedureof dissolving the polymer in THF and pouring in 1 liter of hexane forprecipitation was repeated twice, after which the polymer was separatedand dried. There was obtained 13.6 g of a white polymer, which was foundto have a Mw of 9,600 as measured by the light scattering method, and adispersity (Mw/Mn) of 1.4 as determined from the GPC elution curve. On¹H-NMR analysis, the polymer was found to consist of respective unitsderived from Monomer 2, Monomer 5 and Monomer 7 in a molar ratio of0.29:0.30:0.41.

Evaluation

Polymer Transmittance Measurement

The polymers obtained in Polymer Synthesis Examples 1 to 6, designatedPolymers 1 to 6, respectively, were determined for transmittance. Threeother polymers were furnished for comparison purposes. ComparativePolymer 1 is a monodisperse polyhydroxystyrene having a molecular weightof 10,000 and a dispersity (Mw/Mn) of 1.1 in which 30% of hydroxylgroups are replaced by tetrahydropyranyl groups. Similarly, ComparativePolymer 2 is polymethyl methacrylate having a molecular weight of 15,000and a dispersity (Mw/Mn) of 1.7; and Comparative Polymer 3 is a novolacpolymer having a meta/para ratio of 40/60, a molecular weight of 9,000and a dispersity (Mw/Mn) of 2.5.

Each polymer, 1 g, was thoroughly dissolved in 20 g of PGMEA, and passedthrough a 0.2-μm filter, obtaining a polymer solution. The polymersolution was spin coated onto a MgF₂ substrate and baked on a hot plateat 100° C. for 90 seconds, forming a polymer film of 100 nm thick on thesubstrate. Using a vacuum ultraviolet spectrometer (VUV-200S by NihonBunko Co., Ltd.), the polymer film was measured for transmittance at 248nm, 193 nm and 157 nm. The results are shown in Table 1.

TABLE 1 Transmittance (%) 248 nm 193 nm 157 nm Polymer 1 99 93 72Polymer 2 99 93 67 Polymer 3 99 10 63 Polymer 4 99 93 71 Polymer 5 99 9366 Polymer 6 99 10 62 Comparative Polymer 1 90 5 15 Comparative Polymer2 91 80 12 Comparative Polymer 3 82 6 17

It is evident from Table 1 that resist materials using the inventivepolymers maintain sufficient transparency at the F₂ laser wavelength(157 nm).

Resist Preparation and Exposure

Resist solutions were prepared in a conventional manner by dissolvingamounts as shown in Table 2 of the polymer, photoacid generator (PAG1 orPAG2), basic compound, and dissolution inhibitor (DRI1) in 1,000 partsof PGMEA.

On silicon wafers having a film of DUV-30 (Brewer Science) coated to athickness of 85 nm, the resist solutions were spin coated, then baked ona hot plate at 120° C. for 90 seconds to give resist films having athickness of 100 nm.

The resist films were exposed by means of an F₂ excimer laser exposuretool (VUVES-4500 by Litho Tech Japan Corp.) while varying the exposuredose. Immediately after exposure, the resist films were baked (PEB) at120° C. for 90 seconds and then developed for 60 seconds with a 2.38%aqueous solution of tetramethylammonium hydroxide. The film thicknesswas measured in different dose areas. From the residual filmthickness-to-dose relationship, the sensitivity (Eth) was determined asthe exposure dose giving a film thickness 0. A γ value which was theslope (tan θ) of the characteristic curve was also determined.

Separately, through a mask having a Cr pattern formed on a MgF₂substrate, the resist film in close contact with the Cr pattern surfacewas exposed to a F₂ laser for effecting contact exposure. The exposurewas followed by similar PEB and development, forming a pattern. A crosssection of the pattern was observed under SEM, the ascertainable minimumpattern size giving a resolution.

TABLE 2 Photoacid Basic Dissolution Polymer generator compound inhibitorSolvent Eth, (pbw) (pbw) (pbw) (pbw) (pbw) mJ/cm² γ Polymer 1 PAG1tributylamine — PGMEA 18  8.9 (100) (4) (0.1) (1000) Polymer 2 PAG1tributylamine — PGMEA 14 10.5 (100) (4) (0.1) (1000) Polymer 3 PAG1tributylamine — PGMEA 12 10.9 (100) (4) (0.1) (1000) Polymer 4 PAG1tributylamine — PGMEA 13  9.3 (100) (4) (0.1) (1000) Polymer 5 PAG1tributylamine — PGMEA 11 10.8 (100) (4) (0.1) (1000) Polymer 6 PAG1tributylamine — PGMEA 9 10.5 (100) (4) (0.1) (1000) Polymer 2 PAG1triethanolamine — PGMEA 16 10.3 (100) (4) (0.1) (1000) Polymer 2 PAG1tributylamine DRI1 PGMEA 12 10.1 (100) (4) (0.1) (10) (1000) Polymer 2PAG2 tributylamine — PGMEA 10 12.9 (100) (4) (0.1) (1000) ComparativePAG1 triethanolamine — PGMEA non-sensitive, — Polymer 1 (4) (0.1) (1000)turned (100) negative without film thickness decreasing to 0 nm

Upon exposure to VUVES, the resist compositions within the scope of theinvention exhibited high gamma values and high contrast and exerted thepositive working effect that the film thickness decreased with anincreasing exposure dose. The resolving power upon contact exposure washigh.

Dry Etching Test

A polymer solution was prepared by thoroughly dissolving 2 g of each ofPolymers 1 to 6 in 10 g of PGMEA and passing the solution through a0.2-micron size filter. The polymer solution was spin coated to asilicon substrate and baked to form a polymer film of 300 nm thick. Thewafer having the polymer film formed thereon was subjected to dryetching under two sets of conditions. A first etching test with CHF₃/CF₄gas was performed using a dry etching instrument TE-8500P by TokyoElectron K.K. A second etching test with Cl₂/BCl₃ gas was performedusing a dry etching instrument L-507D-L by Nichiden Anerba K.K. Adifference in polymer film thickness before and after the etching testwas determined. The etching conditions are shown in Table 3, and theresults in Table 4.

TABLE 3 CHF₃/CF₄ gas Cl₂/BCl₃ gas Chamber pressure (Pa) 40.0 40.0 RFpower (W) 1,300 300 Gap (mm) 9 9 Gas flow rate (ml/min) CHF₃: 30 Cl₂: 30CF₄: 30 BCl₃: 30 Ar: 100 CHF₃: 100 O₂: 2 Time (sec) 30 30

TABLE 4 CHF₃/CF₄ gas Cl₂/BCl₃ gas etching rate etching rate Polymer(nm/min) (nm/min) Polymer 1 220 280 Polymer 2 210 260 Polymer 3 170 200Polymer 4 205 235 Polymer 5 190 225 Polymer 6 155 170

It is evident from Table 4 that the resist compositions within the scopeof the invention are fully resistant to dry etching.

Japanese Patent Application No. 2003-032584 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A sulfonate compound having the following general formula (1):

wherein R¹ to R³ each are fluorine or a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, at least oneof R¹ to R³ contains fluorine, R¹ and R², R¹ and R³, or R² and R³, takentogether, may form a ring, each of R¹ to R³ is a straight or branchedalkylene or fluorinated alkylene group of 1 to 18 carbon atoms, whenthey form a ring.
 2. A polymer comprising recurring units of thefollowing general formula (2) and having a weight average molecularweight of 1,000 to 500,000,

wherein R¹ to R³ each are fluorine or a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, at least oneof R¹ to R³ contains fluorine, R¹ and R², R¹ and R³, or R² and R³, takentogether, may form a ring, each of R¹ to R³ is a straight or branchedalkylene or fluorinated alkylene group of 1 to 18 carbon atoms, whenthey form a ring.
 3. A polymer comprising recurring units of thefollowing general formula (2) and recurring units of at least one typeselected from the following general formulae (3a) to (3f) and having aweight average molecular weight of 1,000 to 500,000,

wherein R¹ to R³ each are fluorine or a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, at least oneof R¹ to R³ contains fluorine, R¹ and R², R¹ and R³or R² and R³, takentogether, may form a ring, each of R¹ to R³ is a straight or branchedalkylene or fluorinated alkylene group of 1 to 18 carbon atoms, whenthey form a ring,

wherein R⁴, R⁵, R⁷, R⁸ and R¹⁵ each are a single bond or a straight,branched or cyclic alkylene or fluorinated alkylene group of 1 to 20carbon atoms, R⁶, R⁹, R¹² and R¹⁸ each are hydrogen or an acid labilegroup, R¹⁰, R¹¹, R¹³, R¹⁴, R¹⁶ and R¹⁷ each are hydrogen, fluorine, astraight, branched or cyclic alkyl or fluorinated alkyl group of 1 to 20carbon atoms, at least one of R¹⁶ and R¹⁷ contains at least one fluorineatom, R¹⁹ is a straight, branched or cyclic fluorinated alkyl group of 1to 20 carbon atoms, “a” and “b” each are 1 or
 2. 4. A polymer comprisingrecurring units of the following general formula (2) and recurring unitsof the following general formula (4) and having a weight averagemolecular weight of 1,000 to 500,000,

wherein R¹ to R³ each are fluorine or a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, at least oneof R¹ to R³ contains fluorine, R¹ and R², R¹ and R³, or R² and R³, takentogether, may form a ring, each of R¹ to R³ is a straight or branchedalkylene or fluorinated alkylene group of 1 to 18 carbon atoms, whenthey form a ring,

wherein R²⁰ is a methylene group, oxygen atom or sulfur atom, R²¹ to R²⁴each are hydrogen, fluorine, —R²⁵—OR²⁶, —R²⁵—CO₂R²⁶ or a straight,branched or cyclic alkyl or fluorinated alkyl group of 1 to 20 carbonatoms, at least one of R²¹ to R²⁴ containing —R²⁵—OR²⁶ or —R²⁵CO₂R²⁶,R²⁵ is a single bond or a straight, branched or cyclic alkylene orfluorinated alkylene group of 1 to 20 carbon atoms, R²⁶ is hydrogen, anacid labile group, adhesive group or a straight, branched or cyclicfluorinated alkyl group of 1 to 20 carbon atoms which may contain ahydrophilic group,3 and c is 0 or
 1. 5. The polymer of claim 4 whereinsaid recurring units of formula (4) have a structure of the followinggeneral formula (4a) or (4b):

wherein R²⁶ is as defined above, R²⁷ to R³⁰ each are hydrogen, fluorineor an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms, at leasteither one of R²⁷ and R²⁸ contains at least one fluorine atom, and atleast either one of R²⁹ and R³⁰ contains at least one fluorine atom. 6.A polymer comprising recurring units of the following general formula(2) and recurring units of at the following general formula (5) andhaving a weight average molecular weight of 1,000 to 500,000,

wherein R¹to R³ each are fluorine or a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, at least oneof R¹ to R³ contains fluorine, R¹ and R², R¹ and R³ or R² and R³, takentogether, may form a ring, each of R¹ to R³ is a straight or branchedalkylene or fluorinated alkylene group of 1 to 18 carbon atoms, whenthey form a ring,

wherein R³¹ is hydrogen, fluorine or a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, R³² is asingle bond or a straight, branched or cyclic alkylene or fluorinatedalkylene group of 1 to 20 carbon atoms, R³³ is hydrogen or an acidlabile group, R³⁴ is fluorine or a straight, branched or cyclicfluorinated alkyl group of 1 to 20 carbon atoms, d is 1 or 2, and e isan integer of 0 to 4, satisfying 1≦d+e≦5.
 7. The polymer of claim 6wherein the recurring units of formula (5) have the following formula(5a) or (5b):

wherein R³³ is as defined above, R³⁵ to R⁴⁰ each are hydrogen, fluorineor an alkyl or fluorinated alkyl group of 1 to 4 carbon atoms, at leasteither one of R³⁵ and R³⁶ contains at least one fluorine atom, at leasteither one of R³⁷ and R³⁸ contains at least one fluorine atom, and atleast either one of R³⁹ and R⁴⁰ contains at least one fluorine atom. 8.A polymer comprising recurring units of the following general formula(2) and recurring units of the following general formula (6) and havinga weight average molecular weight of 1,000 to 500,000,

wherein R¹ to R³ each are fluorine or a straight, branched or cyclicalkyl or fluorinated alkyl group of 1 to 20 carbon atoms, at least oneof R¹ to R³ contains fluorine, R¹ and R², R¹ and R³, or R² and R³, takentogether, may form a ring, each of R¹ to R³ is a straight or branchedalkylene or fluorinated alkylene group of 1 to 18 carbon atoms, whenthey form a ring,

wherein R⁴¹to R⁴³ each are hydrogen, fluorine or a straight, branched orcyclic alkyl or fluorinated alkyl group of 1 to 20 carbon atoms, and R⁴⁴is hydrogen, an acid labile group, an adhesive group or a straight,branched or cyclic fluorinated alkyl group of 1 to 20 carbon atoms whichmay contain a hydrophilic group such as hydroxyl.
 9. The polymer ofclaim 8 wherein R⁴³ in formula (6) is trifluoromethyl.
 10. A resistcomposition comprising the polymer of claim
 2. 11. A chemicallyamplified positive resist composition comprising (A) the polymer ofclaim 2, (B) an organic solvent, and (C) a photoacid generator.
 12. Theresist composition of claim 11, further comprising (D) a basic compound.13. The resist composition of claim 11, further comprising (E) adissolution inhibitor.
 14. A process for forming a resist patterncomprising the steps of: applying the resist composition of claim 10onto a substrate to form a coating, heat treating the coating and thenexposing it to high-energy radiation in a wavelength band of 100 to 180nm or 1 to 30 nm through a photomask, and optionally heat treating theexposed coating and developing it with a developer.
 15. The patternforming process of claim 14 wherein the high-energy radiation is an F₂laser beam, Ar₂ laser beam or soft x-ray.
 16. A chemically amplifiedpositive resist composition comprising (A) the polymer of claim 3, (B)an organic solvent, and (C) a photoacid generator.
 17. A chemicallyamplified positive resist composition comprising (A) the polymer ofclaim 4, (B) an organic solvent, and (C) a photoacid generator.
 18. Achemically amplified positive resist composition comprising (A) thepolymer of claim 6, (B) an organic solvent, and (C) a photoacidgenerator.
 19. A chemically amplified positive resist compositioncomprising (A) the polymer of claim 8, (B) an organic solvent, and (C) aphotoacid generator.